ВИНОРОБСТВО І ВИНОГРАДАРСТВО У

Простежено розвиток і проаналізовано чинники, що на нього впливали, виноградарської і виноробної галузі сільського господарства Буджаку (Південної Бессарабії) наприкінці ХІХ - на початку ХХ ст. на документах фонду Аккерманської повітової земської управи Ізмаїльського архіву.There are investigated and analysed factors of development of vine branch of the agriculture of Budchack (South Bessarabia) at the end of XIX – beginning of XX cent. based on the documents of Accerman zemskoy upravy of Ismail archive

Large-scale volumetric flow measurement in a pure thermal plume by dense tracking of helium-filled soap bubbles

We present a spatially and temporally highly resolved flow measurement covering a !arge volume (~o.6 m3) in a pure thermal plume in air. The thermal plume develops above an extended heat source and is characterized by moderate velocities (U~0.35 m/s) with a Reynolds number of Re~500 and a Rayleigh number of Ra~100000. We demonstrate the requirements and capa bilities of the measurement equipment and the particle tracking approach to be able to probe measurement volumes up to and beyond one cubic meter. The use of !arge tracer particles (300 µm), helium-filled soap bubbles (HFSBs), is crucial and yields high particle image quality over large-volume depths when illuminated with arrays of pulsed high-power LEDs. The experimental limitations of the HFSBs-their limited lifetime and their intensity loss over time-are quantified. The HFSBs' uniform particle images allows an accurate reconstruction of the flow using Shake-The-Box particle tracking with high partlcle concentrations up to 0.1 particles per pixel. This enables tracking of up to 275,000 HFSBs simultaneously. After interpolating the scattered data onto a regular grid with a Navier-Stokes regularization, the velocity field of the thermal plume reveals a multitude of vortices with a smooth temporal evolution and a remarkable coherence in time (see animation, supplementary data). Acceleration fields are also derived from interpolated particle tracks and complement the flow measurement. Additionally, the flow map, the basis of a !arge dass of Lagrangian coherent structures, is computed directly from observed particle tracks. We show entrainment regions and coherent vortices of the thermal plume in the flow map and compute fields of the finite-time Lyapunov exponent

High aerodynamic lift from the tail reduces drag in gliding raptors

Many functions have been postulated for the aerodynamic role of the avian tail during steady-state flight. By analogy with conventional aircraft, the tail might provide passive pitch stability if it produced very low or negative lift. Alternatively, aeronautical principles might suggest strategies that allow the tail to reduce inviscid, induced drag: if the wings and tail act in different horizontal planes, they might benefit from biplane-like aerodynamics; if they act in the same plane, lift from the tail might compensate for lift lost over the fuselage (body), reducing induced drag with a more even downwash profile. However, textbook aeronautical principles should be applied with caution because birds have highly capable sensing and active control, presumably reducing the demand for passive aerodynamic stability, and, because of their small size and low flight speeds, operate at Reynolds numbers two orders of magnitude below those of light aircraft. Here, by tracking up to 20,000, 0.3 mm neutrally buoyant soap bubbles behind a gliding barn owl, tawny owl and goshawk, we found that downwash velocity due to the body/tail consistently exceeds that due to the wings. The downwash measured behind the centreline is quantitatively consistent with an alternative hypothesis: that of constant lift production per planform area, a requirement for minimizing viscous, profile drag. Gliding raptors use lift distributions that compromise both inviscid induced drag minimization and static pitch stability, instead adopting a strategy that reduces the viscous drag, which is of proportionately greater importance to lower Reynolds number fliers

Investigation of the wake of low aspect ratio cylinders by tomographic PIV

The wakes of wall mounted circular cylinders of very low aspect ratio have been investigated in a wind tunnel. Besides planar PIV, also high resolution tomographic PIV was used to capture the flow phenomena downstream of the cylinder. By changing the velocity U_inf and the cylinder height h at a constant aspect ratio h/D, a wide database of different flow conditions was obtained. The resulting relative height of the boundary layer thickness was between h/delta=0.6 and h/delta=2.5, while the Reynolds number based on the length l between leading edge and cylinder centre Re_l was between Re_l=57,000 and Re_l=188,000. A pair of counter-rotating vortices was found in the wake of the cylinder. The rotation sense is such, that in the center of the wake a positive vertical velocity component results. Also horseshoe vortices were found next to these trailing vortices. The relative height of the incoming boundary layer has a large impact on the development, strength and dissipation of the vortex system

Untersuchung von turbulenten Strömungsstrukturen in einer Plattengrenzschicht mit Hilfe von 4D-PIV

Die Untersuchung der Topologien von kohärenten Geschwindigkeitsstrukturen in turbulenten Plattengrenzschichten hatte mit dem Aufkommen der PIV Messtechnik eine wertvolle Datenquelle erhalten. Die seit Mitte der 90er Jahre in Form von digitalem Stereo PIV entwickelte Messtechnik ermöglicht die Bestimmung von momentanen 3C-Geschwindigkeitsvektorfeldern in je einer Ebene der Strömung. Neueste Entwicklungen waren durch technische Restriktionen entweder in Richtung Zeit- oder Raumauflösung (Holo-, Multiplane-, Scanning-PIV, HS-PIV etc.) beschränkt. Für die Analyse der zeitlichen und räumlichen Entwicklung von Strömungsstrukturen wäre eine entsprechend auflösende (optische) Messtechnik der Bestimmung von zeitlich aufgelösten, momentanen Geschwindigkeitsvektorvolumen (4D-Vektorvolumen) in künstlich gestörten Plattengrenzschichtströmungen (Turbulenter Spot, „getrippte“ turbulente Grenzschicht)